James M. Buchanan’s and Vincent Ostrom’s contributions to the field of Constitutional Political Economy spanned 60+ years as they explored how individuals come together in democratic societies to design social decision processes capable of protecting individual liberty. This chapter examines a set of rules frequently associated with such protective processes—votes, vetoes, voice, and exit—in order to compare how these scholars’ approaches to constitutional choice overlapped and where their perspectives differed slightly. It concludes with an examination of their treatments of US federalism and their concerns for the future viability of this institutional form.